Hi @ngreen ,
Do you want to add new Choice options to the Choice field in your SP List through PowerApps app?
If you want to add new Choice options to the Choice field in your SP List itself through PowerApps app, I afraid that there is no way to achieve your needs in PowerApps currently.
As an alternative solution, you could consider add custom option value via typing search text within the Choice field ComboBox directly. The screenshot as below:

Set the OnStart property of App to following:
Clear(ChoiceCollection);
ClearCollect(ChoiceCollection, Choices([@'Your SP List'].ChoiceField));
ForAll(
Filter(Distinct('Your SP List', 'Trip Status'.Value),!IsBlank(Result)),
If(
Not(Result in ChoiceCollection.Value),
Collect(ChoiceCollection, Result)
)
)
Set the Update property of the Choice field Data card to following:
If(
!IsBlank(DataCardValue15.Selected),
DataCardValue15.Selected,
!IsBlank(DataCardValue15.SearchText),
{
Value: DataCardValue15.SearchText
}
)
Set the Items property of the Choice field ComboBox to following:
ChoiceCollection
Set the OnSuccess property of Edit form to following:
Clear(ChoiceCollection);
ClearCollect(ChoiceCollection, Choices([@'Your SP List'].ChoiceField));
ForAll(
Filter(Distinct('Your SP List', 'Trip Status'.Value),!IsBlank(Result)),
If(
Not(Result in ChoiceCollection.Value),
Collect(ChoiceCollection, Result)
)
);
Back()
Please take a try with above solution, then re-load your app, check if it could help in your scenario.
Best regards,